A proposal is made in this application for sponsorship of a Conference to be held in Chicago in January, 1976 on radiation associated thyroid cancer. The Conference is visualized as a working meeting. Individuals actively operating recall programs attempting to find patients with prior head and neck radiation, individuals with long experience with the problems of radiation associated thyroid cancer, and experts in the fields of nuclear medicine, thyroid cancer, and diagnostic techniques would be invited, and others would be offered the opportunity to attend. The Conference would deal specifically with problems involved in patient finding, mechanics of operating a recall program, appropriate diagnostic measures to be used, appropriate interpretations of scans, delineation of the lower and upper threshold of significant radiation exposure, selection of the most appropriate surgical procedure, the utility of thyroid hormone suppression of thyroid function, and follow-up mechanisms. An attempt would be made to obtain consensus of the group on specific approaches to handling detection, treatment, and prevention of radiation associated thyroid tumors. It is estimated that several hundred thousand patients in the United States may have had significant head or neck exposure, and a large fraction of these will be examined in the coming years. It is believed imperative to delineate the appropriate medical response that will guard these patients against tumor development, without subjecting them to excessive tests or surgical procedures. The expense accounts of the Conference would include general expenses for invited speakers, use of the facilities, and secretarial assistance for development of the Conference and publication of a report.